Synthesis of enantioenriched .alpha.-hydroxy-.alpha.-allenylacetic acids by [2,3] Wittig rearrangement of .alpha.-(propargyloxy)acetates

作者: James A. Marshall , Xiao Jun Wang

DOI: 10.1021/JO00016A020

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摘要: Optically active (R)-(propargyloxy) acetic esters 5, available in ca. 90% ee through reduction of alkynones 2 with Chirald-LiAlH 4 followed by alkylation chloroacetic acid and esterification CH N , undergo highly stereoselective [2,3] rearrangement upon treatment LDA THF at −78 o C Cp ZrCl to afford α(S)-hydroxy-β(R)-allenic 7 complete transfer chirality >90% diastereoselectivity. Upon TESOTf Et 3 the 5 diastereomeric α-(R)-hydroxy-β-(R)-allenic 8 stereoselectively. Both hydroxy cyclize stereospecifically trans- cis-2,5-dihydrofurans 13-15 17-19 AgNO -CaCO PhSeCl, or NBS

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